Object and method for providing efficient multi-user access to shared operating system kernal code using instancing

• US 6,023,749 A
• Filed: 01/25/1999
• Issued: 02/08/2000
• Est. Priority Date: 01/07/1997
• Status: Expired due to Term

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Inventors: Richardson, John J.
• Primary Examiner(s): Cabeca, John W.
• Assistant Examiner(s): Chow, Christopher S.
• Application Number:
  US09/236,928
• Time in Patent Office: 379 Days
• Field of Search: 395/674, 711/147, 711/150, 711/173, 711/153, 709/104
• US Class Current: 711/203
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system

Abstract

A method for improving the performance of a multi-user operating system includes the steps of providing a kernal mode memory region in which instantiations of kernal objects associated with each user may be stored. Each instantiations of a particular kernal object is accessed via the same virtual address. Storing instantiations of kernal objects reduces code contention for commonly used kernal objects while allowing the instantiation to retain kernal mode protections.

Claims

1. In a computer system servicing at least a first user and a second user and including an operating system having a kernal memory space for storing protected code, an apparatus for improving the performance of the system comprising:

a kernal mode memory region of the kernal memory space reserved for storing instantiations of kernal objects;

a first instantiation of a kernal object stored in a first range of physical memory addresses in the kernal mode memory region and associated with the first user of the system;

a second instantiation of the kernal object stored in a second range of physical memory addresses in the kernal mode memory region and associated with the second user of the system; and

a page table for each user of the system, wherein each page table stores a mapping between a virtual memory address that is common for each instantiation of the kernal object and each range of physical memory addresses in the kernal mode memory region occupied by each instantiation of the kernal object.

2. The apparatus of claim 1 further comprising a page directory that stores a mapping of the page table for the first user and at least one process associated with the first user.

3. The apparatus of claim 1 wherein the first and second ranges of physical memory addresses in the kernal mode memory region are identical when a plurality of users access but do not attempt to write to that memory location.

4. The apparatus of claim 1 wherein the first and second ranges of physical memory addresses in the kernal mode memory region differ when a plurality of users attempt to write to the first range of physical memory addresses.

5. The apparatus of claim 1 comprises a data structure storing data that indicates whether the first range of physical memory addresses in the kernal mode memory region can be shared by a plurality of instantiations of the kernal object.

6. The apparatus of claim 1 wherein the first and second ranges of physical memory addresses in the kernal mode memory region are dynamically reserved upon the occurrence of a predetermined event.

7. The apparatus of claim 6 wherein the predetermined event is when the second user logs onto the computer system.

8. The apparatus of claim 6 wherein the predetermined event corresponds to a start-up sequence of the computer system.

9. A method for providing a first user and a second user of a computer system concurrent access to shared, writeable operating system kernal code, the method comprising:

(a) allocating a first region of kernal mode memory space for the first user and a second region of kernal mode memory space for the second user;

(b) forming a first instantiation of a computer kernal object associated with the first user of the computer system;

(c) forming a second instantiation of the computer kernal object associated with the second user of the computer system;

(d) storing the first kernal object instantiation in the first kernal mode memory region and the second kernal object instantiation in the second kernal mode memory region; and

(e) accessing a data structure associated with each user of the computer system for obtaining a mapping between a virtual memory address that is common for each instantiation of the computer kernal object and a physical memory address of the first and second kernal object instantiations in the kernal mode memory space.

10. The method of claim 9 comprising the step of accessing a page directory to obtain a location of the data structure associated with the first user when executing at least one process associated with the first user.

11. The method of claim 9 further comprising the step of determining from the data structure whether the physical memory address associated with the first kernal object instantiation can be accessed by a plurality of other kernal object instantiations.

12. The method of claim 9 comprising the step of dynamically allocating the first and second regions of kernal mode memory space in response to the occurrence of a predetermined event.